This invention relates to a topsheet made of nonwoven fabric having a plurality of fine openings suitable for use as a breathable topsheet material or a breathable and liquid-pervious topsheet material in a disposable wearing article such as a disposable diaper, a disposable sanitary napkin, a disposable incontinent pants or a disposable gown used in medical facilities.
Japanese Patent Application Publication No. 1986-176346A describes a topsheet made of a nonwoven fabric adapted to be used in an absorbent article. This topsheet is formed by thermally fusible hydrophobic fibers having a fiber diameter smaller than 10xcexc and a basis weight of 10 g/m2. The topsheet has an opening ratio of 10-50% and the minimum opening diameter of 0.3-2 mm wherein the fibers are in a melted state around the openings.
Japanese Patent Application Publication No. 1988-243360A describes a nonwoven fabric having a plurality of fine openings arranged in a given pattern. This nonwoven fabric has a nonwoven fabric region with of circular or elliptic openings a wherein the nonwoven fabric region has a substantially uniform density of fiber and a substantially smooth surface. The nonwoven fabric with the above-described openings is made by applying high pressure water-jets in columnar streams to a fibrous web supported on a cylinder having a plurality of projections in semispherical shape.
The nonwoven fabric disclosed in each of the above-identified Publication is intended to be used as a liquid-pervious topsheet in disposable wearing article such as a disposable diaper or a sanitary napkin. The openings formed in the nonwoven fabric are a means to enhance transfer and absorption of body fluids into a liquid-absorbent core covered with this nonwoven fabric. However, when a the wearing article using such nonwoven fabric is worn, the nonwoven fabric having a smooth surface and the wearer""s skin may come in close contact with each other so that most of the openings may be closely covered with the wearer""s skin and thereby rapid absorption of body fluids may be obstructed. In addition, such close contact of the nonwoven fabric with the wearer""s skin may often cause stuffiness and eruption of the wearer""s skin.
The present invention provides a nonwoven fabric that overcomes problems that possibly occur in prior art nonwoven fabrics when used as a topsheet of a disposable wearing article.
It is an object of the present invention to provided a topsheet made of a nonwoven fabric for a disposable wearing article having upper and lower surfaces and formed with a plurality of openings extending through the upper and lower surfaces.
The topsheet has a substantially uniform thickness and each of the openings has an area of about 0.16-5 mm2 wherein only a part of the periphery of the opening is increased in thickness compared to the uniform thickness of the topsheet so as to make the openings protuberate upward from the upper surface.